Push pins or thumbtacks (collectively referred to herein as "push pins") are used to secure pieces of paper, photographs, postcards, posters and similar items on a support surface, such as a wall, ceiling or bulletin board. Conventional push pins typically have a head and a pin. The head generally has a planar base and is usually formed of metal or injection molded plastic. The pin has first and second ends, wherein the first end is shaped into a point for insertion into the support surface. The second end of the pin is attached to or anchored within the head such that the pin projects outwardly from the base of the head.
When securing an item to a support surface using one or more conventional push pins, the item is first positioned on the support surface in a pre-selected location and orientation. Thereafter, the item is secured to the support surface by inserting the corresponding pin of one or more push pins through the item and into the support surface. To firmly anchor each push pin within the support surface, the entire portion of the pin that projects beyond the base of the head is usually inserted into the support surface. Although the portion of the item surrounding the pin may be positioned between the base of the head and the support surface, the item is primarily secured in place by the pin, especially where the item is secured to a support surface having a vertical orientation, such as a wall or bulletin board mounted to a wall.
As the pin of a push pin pierces through the item, the pin creates a hole or opening in the item. Over time, this hole can expand due to the weight of the item bearing against the pin and, in some instances, can even result in a tear forming in the item. In either case, the effectiveness of the push pin to secure the item to the support surface can be diminished. In addition, where the item is of value or is to be reused, for example, a photograph, the damage caused by the pin of the push pin is not only aesthetically displeasing, but may be irreparable.
In seeking better apparatuses for securing items to a support surface, several types of tacks have been proposed. One such example is disclosed in U.S. Pat. No. 5,199,681 to Reidy, which discloses an L-shaped framing tack used to frame square or rectangular items, such as charts, certificates, posters, and maps. The tack has a unitary body portion that includes first and second perpendicularly disposed arms. The underside of each arm has a ridge extending along the outer edge of the arm such that the interior surface of each arm is recessed. A pin projects outwardly from the underside of the body portion at the intersection of the raised outer edges of the first and second arms. At the intersection of the first and second arms, the body portion also includes a flange that extends between the raised outer edges of the arms and which is spaced apart from the recessed interior surfaces of the arms. The spaced region or slot defined between the flange and the recessed interior surfaces of the arms is adapted to removably receive the corner of an item and a locking mechanism. The locking mechanism includes a base defining a groove and ridge and a slidable top portion defining a corresponding groove and ridge. When the top portion is slid into a position such that the ridge of the top portion is seated within the groove of the base, the locking mechanism is in the unlocked position and can be removed from the slot. When the locking mechanism is inserted into the slot and the top portion is slid into a position such that the ridge of the top portion is seated on the ridge of the base, the locking mechanism is in the locked position and is wedged between the flange and the recessed interior surfaces of the arms.
An item is secured to a support surface using a set of four L-shaped tacks by inserting each corner of the item into the slot defined between the flange and recessed interior surface of the first and second arms of a corresponding tack. The corresponding locking mechanism is then inserted into the slot such that the base of the locking mechanism is pressed against the corner of the item. The top portion of the locking mechanism is then slid into the lock position thereby securing the corner of the item between the base of the locking mechanism and the recessed interior surface of the first and second arms. The pin of each tack is then inserted into the support surface. The L-shaped framing tacks are effective in securing square or rectangular items that have corners, but not circular or other curvilinear items. In addition, the body portion is relatively flat, which can make the tacks difficult to grip when inserting or withdrawing the tacks.
Thus, there is a need for an improved push pin for use in securing items to a support surface. The push pin must be capable of securing an item to the support surface without puncturing or otherwise damaging the item. The push pin must also be capable of securing items having square, rectangular and curvilinear geometries. Additionally, the head of the push pin should facilitate gripping by the user when inserting and withdrawing the push pin into and out of the support surface, respectively.